Air-bag

ABSTRACT

A side air-bag for use in a motor vehicle is disclosed. The side air-bag is formed from two superimposed layers of a lamina material such as fabric. Each layer has a leading edge and a trailing edge. The air-bag includes at least one internal tether which extends from the leading edge to the trailing edge, with the length d of the tether being less than the width D of the elements forming the airbag between the leading edge and a trailing edge at a point where the tether is positioned.

THE PRESENT INVENTION relates to an air-bag for use in a vehicle such asa motor car and more particularly relates to a side air-bag.

A side air-bag may be mounted in position, for example, in the backrestof a vehicle seat or in part of the side wall or a side door of themotor vehicle, the air-bag being configured, when inflated, to belocated between the occupant of a seat and the adjacent side of thevehicle.

A side air-bag may prove to be of particular benefit in a side impactsituation. However, in a side impact situation an intruding vehicle orobject can, even at relatively low speeds, impact with an occupant ofthe vehicle very shortly after the impact situation has commenced, andconsequently it is desirable to be able to inflate a side air-bag in theminimum amount of time. Consequently it is desirable to be able toinflate the side air-bag using a minimum quantity of gas.

However, it is also desired that a side air-bag should be as thick or“deep” as possible in the traverse direction across the vehicle, inorder to provide the maximum cushioning effect for the occupant of avehicle relative to an intruding vehicle or object.

Consequently it is desired to provide a side air-bag which can beinflated quickly using a minimum quantity of gas, but which has arelatively high thickness or “depth”.

The present invention seeks to provide an improved side air-bag.

According to the present invention, there is provided a side air-bag foruse in a motor vehicle, the side air-bag being formed from twosuperimposed layers of a laminar material, each layer having a leadingedge and a trailing edge, there being at least one internal tetherhaving opposed ends connected to the leading edge and the trailing edge,the length of the tether between the connections being less than thewidth of the said layers forming the air-bag between the saidconnections.

Preferably when the side air-bag is mounted in the motor vehicle, the oreach tether is configured to extend in a direction substantiallyparallel to the longitudinal axis of the motor vehicle when the air-bagis inflated.

Advantageously there is a single tether.

Conveniently there are at least two tethers at spaced apart positions.

Preferably the air-bag is divided into two separate internal inflatablechambers by means of a seam interconnecting the said layers of laminarmaterial.

Advantageously the width of each said layer of laminar material at thepoint where the tether is provided is W and the length of the or eachtether is d, wherein d<2W/π.

In order that the invention may be more readily understood, and so thatfurther features thereof may be appreciated, embodiments of theinvention will now be described, by way of example, with reference tothe accompanying drawings in which:

FIG. 1 is a plan view illustrating two components for forming anair-bag.

FIG. 2 is a view of an air-bag formed from the components of FIG. 1illustrating additionally a gas generator and deflector;

FIG. 3 is a view of a modified embodiment to the invention; and

FIG. 4 is a view of a modified air-bag similar to that shown in FIG. 2.

Referring initially to FIG. 1 of the accompanying drawings, an element 1of flexible laminar material such as fabric, is illustrated. It is to beunderstood that two components of the shape and form of the element 1are to be superimposed and joined together to form an air-bag.Alternatively a single component of appropriate shape may be foldedabout a fold line to provide the two superimposed elements.

The element 1 has a central substantially rectangular region 2 withrounded comers. The rectangular region 2 has a leading or forward edge 3and a trailing or rearward edge 4. The forward edge 3 forms that part ofthe air-bag which will be towards the front of the vehicle when theair-bag is in position in the vehicle and inflated, and the rearwardedge 4 is the edge of the air-bag which will be towards the rear of thevehicle when the air-bag is in position in the vehicle and inflated.

The rearward or trailing edge 4 is provided with a rearwardly projectingportion 5 located substantially at its mid point. The projecting portion5 is provided with two apertures 6, 7 therein at spaced apart positions.

The overall width of the element 1, from the leading edge 3 to thetrailing edge 4 is a width W.

A further component 8 is illustrated in the form of a tether. Thecomponent 8 is a rectangular element of flexible laminar material suchas fabric. The element has a length d, the length d being such that,preferably, d<2W/π.

In fabricating an air-bag, two elements such as the element 1 aresuperimposed, with a tether 8 inserted between them. The twosuperimposed elements are interconnected by means of a peripheral seam 9as shown in FIG. 2 which extends around the periphery of thesuperimposed elements 1 except for the region at the end of the rearwardprojection 5 formed in the trailing edge 4 of the superimposed layers.The internal tether 8 is secured, adjacent the rearward projection 5, toat least one of the layers 1 by the stitching the seam 9, or forming theseam 9 using some other technique. The leading or forward edge 3 of eachelement 1 is slightly back towards the trailing edge 4 as the air-bag isfabricated so that the leading or forwardmost edge of the tether 8 maybe trapped in the region of the seam adjoining the leading or forwardedges of the elements 1. The two elements, at least in the region of thetether, will be wrinkled and will not lie flat. It is to be understoodthat the width of the fabric of the elements between the points at theleading and trailing edge, where the tether is secured to the fabric, isgreater than the length of the tether between said points, which meansthat some wrinkles or folds must be present in the fabric.

A cylindrical gas generator 10 may be provided to be mounted within theair-bag, the gas generator 10 having a cylindrical body 11 with twoparallel and radially extending studs 12, 13. The cylindrical body 11may be provided with gas outlet apertures 14. In conjunction with thegas generator 10, a protecting element or gas diffuser 15 may beprovided, the protecting element 15 being of open-channel-form and beingprovided with two apertures 16, 17 located and configured to receive thestuds 12, 13. The protector 15 may be mounted on the studs 12, 13 of thegas generator 10 to form a gas generator unit and the thus-assembled gasgenerator unit may be inserted into the air-bag through the openingformed by the un-connected peripheral parts of the superimposed elements1 in the region of the co-aligned rearward projections 5. When the gasgenerator unit has been inserted into the air-bag, the studs 12, 13 maybe passed through the apertures 6, 7 in each of the projections 5, thuseffectively sealing the air-bag.

The air-bag, as thus described, may be mounted in a motor vehicle at asuitable position for the air-bag to act as a side air-bag, and thus theair-bag may be mounted in the backrest of a vehicle seat or in part ofthe side wall of the vehicle adjacent a vehicle seat.

On deployment of the air-bag, gas from the gas generator will beinjected into the air-bag. The effect of the tether 8 will be to preventthe forward or leading edge 3 of the air-bag from moving a substantialdistance in the x direction (or main longitudinal axis) of the motorvehicle (as indicated in FIG. 2) from the rear or trailing edge 4, thusforcing the air-bag to adopt a pre-determined shape on inflation. Itshould be appreciated that the x-direction is the direction of forwardstravel of the motor vehicle. In the absence of an internal tether, suchas the tether 8, the air-bag, if sufficient gas is injected into it,would tend to adopt a generally cylindrical format. However, in view ofthe presence of the tether, the leading or forward edge 3 of the air-bagcannot move sufficiently far away from the rear or trailing edge 4 inthe x direction to form a cylinder, but instead the air-bag is inflatedto have a very substantial thickness or depth in the orthogonaly-direction (transverse with respect to the longitudinal axis of themotor vehicle), whilst not extending very far forwards relative to thegas generator. The y-direction is shown in FIG. 2 extending out of thepage. The air-bag thus provides an optimum dimension in the directionwhere energy is to be absorbed.

FIG. 3 illustrates a modified embodiment of the invention. FIG. 3 showsa complete air-bag 20 which is formed from two substantially identicalsuperimposed elements 21, 22, of flexible laminar material such asfabric although the air-bag could be formed using a one piece weavingtechnique. The air-bag is provided with a peripheral outer seam 23interconnecting the elements 21, 22, and presents a leading edge 24 anda trailing edge 25 in a similar manner to the above-described embodimentof FIGS. 1 and 2. The trailing edge 25 of the air-bag 20 is providedwith a slit or opening 26 through which a gas generator may be insertedinto the interior of the air-bag. The air-bag is also provided with twospaced apart apertures 27, 28 adjacent the slit 26, which aredimensioned to accommodate the studs of a gas generator assembly,equivalent to the studs 12, 13 of the gas generator 10 described withreference to FIG. 2.

The air-bag, in the described embodiment, is divided into two separateinternal inflatable chambers 28, 29 by means of an internal seam 30interconnecting the elements 21, 22.

Two tethers 31, 32 are provided on the interior of the air-bag 20, andagain each tether 31, 32 is such that the length of the tether extendingbetween points of the leading edge 24 and the trailing edge 25 where thetether is connected tot he fabric elements 21, 22 is less than the widthof each of the fabric elements 21, 22 between said points. Again thepurpose of the tethers 31, 32 is to ensure that the air-bag has anappropriate configuration when it is inflated, in a generally similarmanner to the embodiment of FIGS. 1 and 2.

The two tethers 31, 32 of the embodiment of FIG. 3 can either beconfigured to be of equal length to one another or such that they are ofunequal lengths (as illustrated in FIG. 3). By varying the relativelengths of the two tethers 31, 32, different inflation characteristicscan be imparted to the airbag 20.

FIG. 4 shows an air-bag 40 which is similar to the air-bag shown n FIG.2, the air-bag being provided with an internal tether 41 which extendsdiagonally from the forward or leading edge to the trailing edge. Inthis embodiment, although the tether 41 may have a length which isgreater than the width of the air-bag, measured horizontally,nevertheless, the length of the tether between the end parts whichconnected, respectively, to the leading edge and the trailing edge ofthe air-bag is less than the width of each of the two layers forming theair-bag extending between the said two connections. Thus again thefabric of the air-bag is initially wrinkled or folded due to the factthat the length of the tether between the connections is less than thelength of the fabric elements between the connections.

In each of the above-described embodiments, it is to be appreciated thatthe or each tether is only connected to the fabric elements of theair-bag at opposed ends of the tether, so that, when the air-bag isinflated, the tether extends across the interior of the air-bag.

Whilst the invention has been described with reference to embodiments inwhich the tethers are connected to the air-bag by having parts of thetether trapped between superimposed elements of fabric or the like whichare then secured by stitching, with the stitching “trapping” the ends ofthe tethers, the tethers could be held in position in other ways, forexample by using an adhesive.

In the present specification “comprises” means “includes or consists of”and “comprising” means “including or consisting of”.

1. A side air-bag for use in a motor vehicle, the side air-bagcomprising two superimposed layers of a laminar material, each layerhaving a leading edge and a trailing edge, there being at least oneinternal tether having opposed ends connected to the leading edge andthe trailing edge, the length of the tether between the connectionsbeing less than the width of the layers forming the air-bag between theconnections.
 2. A side air-bag according to claim 1 when mounted in amotor vehicle, wherein the or each tether is configured to extend in adirection substantially parallel to the longitudinal axis of the motorvehicle when the air-bag is inflated.
 3. A side air-bag according toclaim 1 wherein there is a single tether.
 4. A side air-bag according toclaim 1 wherein there are at least two tethers at spaced apartpositions.
 5. An air-bag according to claim 1 wherein the air-bag isdivided into two separate internal inflatable chambers by means of aseam interconnecting the layers of laminar material.
 6. An air-bagaccording to claim 1 wherein the width of each layer of laminar materialat the point where the tether is provided is W and the length of the oreach tether is d, wherein d<2W/π.